Crude oil is the number one starting material for the synthesis of key organic chemicals and polymers. As oil becomes increasingly scarce and expensive, biological processing of renewable raw materials in the production of chemicals using live microorganisms or their purified enzymes becomes increasingly interesting. Biological processing, in particular, fermentations have been used for centuries to make beverages. Over the last 50 years, microorganisms have been used commercially to make compounds such as antibiotics, vitamins, and amino acids. However, the use of microorganisms for making industrial chemicals has been much less widespread. It has been realized only recently that microorganisms may be able to provide an economical route to certain compounds that are difficult or costly to make by conventional chemical means.